The inert gases, such as nitrogen, and the rare gases, namely helium, neon, argon, krypton, xenon and mixtures thereof, are commonly employed in a number of industries, in particular the electronics industry. The latter, quite particularly, requires the inert gases to be as pure as possible, and to have their impurities removed, in particular hydrogen and carbon monoxide.
These inert gases are usually produced by cryogenic distillation after liquefaction.
However, the liquefied inert gases obtained in this way generally contain impurities such as hydrogen (H.sub.2) and carbon monoxide (CO), in proportions which are generally greater than a few hundred ppb (parts per billion by volume), or even a few ppm (parts per million by volume), which it is necessary to remove.
A number of processes for purifying inert fluids are known from the prior art, but they generally have several drawbacks or disadvantages, namely:
either they are ill-suited to purifying inert fluids in the liquid state, PA1 or they do not permit purification with respect to the impurities H.sub.2 and/or CO contained in the inert fluid which is to be purified, PA1 or they need the inert fluid to be vaporized prior to its purification. However, it is clear that, when it is desired to obtain an inert fluid in the liquid state which is substantially purified with respect to its impurities H.sub.2 and/or CO, the need to successively vaporize the inert fluid which is to be purified, purify the inert gas, then reliquefy the purified inert gas obtained, represents a major economic drawback, especially as regards energy expenditure and the equipment to be used. PA1 which is easy to use industrially and is of reasonable cost, PA1 which makes it possible to obtain a very high-purity inert fluid in the liquid state, that is to say containing at most about 1 ppb.+-.1 of hydrogen and/or of carbon monoxide, PA1 which can be used at temperatures which are cryogenic for the inert fluids in the liquid state, namely temperatures which are generally lower than -180.degree. C., PA1 which uses inexpensive and/or readily accesible adsorbents, PA1 and which do not require vaporization prior to the purification of the liquid fluid to be purified, then subsequent reliquefaction of the purified fluid. PA1 a) the fluid in the liquid state which is to be purified is passed through at least one bed of particles of at least one adsorbent in order to adsorb at least one of the impurities H.sub.2 and CO contained in the inert fluid in the liquid state; PA1 b) the inert fluid in the liquid state which is substantially purified with respect to at least one of the impurities H.sub.2 and CO is recovered.
Thus, U.S. Pat. No. 3,996,082 describes a process for purifying argon gas with respect to its impurity oxygen, by passing this argon through a synthetic type A zeolite.
For its part, U.S. Pat. No. 2,874,030 describes a process for purifying argon gas with respect to its impurity oxygen, in which the oxygen is converted into water by catalytic reaction with an excess of hydrogen; the water which is formed being subsequently removed using a dehydrating means.
For its part, Patent Application EP-A-0,350,656 describes a process for purifying an inert gas with respect to its impurities oxygen, carbon monoxide and hydrogen, in which the carbon monoxide (CO) and the hydrogen (H.sub.2) that are present in the inert gas are removed by catalytic oxidation at a temperature of between 150.degree. and 250.degree. C. in the presence of a first catalyst based on reduced copper, then of a second catalyst based on oxidized copper, to give carbon dioxide CO.sub.2 and water H.sub.2 O which are subsequently removed by adsorption at ambient temperature on an adsorbent of the molecular sieve type.
Thus, none of the processes which currently exist is suitable for the purification of inert fluids in the liquid state with respect to their impurities hydrogen (H.sub.2) and/or carbon monoxide (CO), that is to say inert fluids liquefied at cryogenic temperature (below their bubble point).
It is therefore necessary to develop novel processes for purifying inert fluids in the liquid state with respect to their impurities H.sub.2 and/or CO.